1. Field of the Invention
The invention concerns a drive point for a substantially tubular, in particular hollow-cylindrical, driven pile having a pile core, through which concrete can be introduced into the driven pile, wherein the drive point can be fitted on to a pile end of the driven pile, wherein at least one first support limb with a first support surface for an end face of the pile end is arranged at an inside wall of the drive point.
2. Description of Related Art
Drive points of that kind are used in the construction industry for making pile foundations. The individual driven piles which generally comprise ductile cast iron and are of predetermined lengths of for example five meters are fitted one into the other to produce a pile foundation. To facilitate inserting driven piles one into each other and thus extending the length of a pile foundation the driven piles usually have a conically tapering first pile end and a second pile end which is shaped to provide a socket. In that way the pile foundation can be driven into the ground pile by pile, whereby it is possible to produce pile foundations of any length quickly and inexpensively. Driven piles of that kind are usually produced in a centrifugal casting process with a shaping rotating mold. That results in substantially cylindrical tubular piles which are internally hollow. Depending on the respective kind of use those hollow-cylindrical driven piles can be filled or encased with concrete or another suitable injection material to produce a stable foundation after having been driven into the ground.
To produce a so-called shaft-grouted pile foundation a drive point is fitted on to the first driven pile, the outside diameter of the drive point being greater than the outside diameter of the driven pile. In that way an annular space can be produced during the driving-in operation, and that space can be filled with the injection material or concrete by a pressure grouting operation. For that purpose, during the driving operation a pumpable concrete mortar which is usually of a grain size of up to 4 mm is conveyed through the hollow pile core of the driven pile to the foot of the pile and pressed into the ground at the drive point. This means that the concrete pressure grouting operation takes place simultaneously with the pile driving operation and is concluded upon the attainment of the final depth of the pile foundation. The shaft grouting operation permits a considerable increase in the useful load of a pile foundation in particular in gravels and sands because a substantially higher level of shaft friction prevails in large-grain grounds between the pressing shaft and the ground, than between the pile tube of an ungrouted driven pile and the ground.
So that the concrete mortar introduced into the pile core of a driven pile can issue from the driven pile and can form a pressed grouting sheathing around the driven pile, it is known in the state of the art for suitable openings to be cut out of the driven pile. That however results in a weakening of the tubular cross-section and thus static instabilities of a pile foundation.